1. Field of the Invention
The present invention pertains to techniques for sealing devices to the interior wall of a surrounding chamber. More particularly, the present invention relates to seals used in conjunction with tray packings in process chambers.
2. Description of Related Art
Many commercial and chemical processes involve mass transfer or heat exchange, and utilize packed columns or chambers to carry out the steps. Such processes can include distillation, absorption and desorption, fractionating, gas cleaning and drying, scrubbing and various biological processes, for example. Two fluids, usually a gas and a liquid, are intermingled within a chamber, typically as countercurrent flow streams wherein the two fluids move generally in opposite senses along the same flow axis.
The mass transfer rates and/or the reaction rates of the processes increase with increasing opportunities for the two fluids to interface with each other. Packing is generally included in exchange process columns to enhance the interaction between two fluids in the column, thereby increasing the efficiency of the process. There are different types of packing systems, depending on the packing elements and their arrangements in the transfer chamber. Structured packing systems generally include extended, structured packing elements that are arranged within the chamber. Random packing systems comprise generally small, individual packing elements that may be dumped into the exchange chamber in a random array. Tray-type systems include multiple packing sections, in which gas and liquid are made to contact, positioned in a vertical array. After interacting with the gas at one such packing section, liquid is passed by a down flow pipe, or downcomer, to a lower section for further contact with the gas, which is passing upwardly in the system.
U.S. Pat. No. 3,179,389 is directed to a tray-type system in which a plurality of fluid contact trays are assembled in a unit that is then inserted into a tower. The trays are thus positioned vertically spaced apart and horizontally oriented. Contact trays disclosed include multiple floating valves that allow gas or vapor to pass upwardly through the tray into contact with liquid on the tray. Each such tray carries a seal for engaging the inner surface of the tower to hold the liquid on the tray. A seal 10 of the type used is illustrated in FIG. 1. The ring seal 10 is a flat, resilient split ring metal seal having a gap 10a. As shown in FIG. 2, a tray deck 12 carries the ring seal 10 about the periphery of the tray in an appropriate groove 14 formed between the offset rim 12a of the tray and an underlying attached ring 16. In its relaxed, expanded state, the ring seal 10 has a greater outer diameter than the diameter of the inner surface of the wall of a process tower 18, as indicated in FIG. 2. The ring seal 10 is forced to a contracted state, reducing its diameter so that the seal passes further into the tray groove 14 to allow the tray 12 to be inserted into the tower 18. The ring seal 10 then engages the inner surface of the tower wall 18 to form a seal between the tray deck 12 and the tower wall, as indicated in FIG. 3. Although the gap 10a is lessened when the ring seal 10 is positioned within a tower 18 with a tray 12, the gap nevertheless remains open, preventing a complete seal around the periphery of the tray with the tower wall. Further, as the tray 12 is passed down into a tower 18, a ring seal of the type 10 may be further compressed by projections on the tower wall 18, which may not be necessarily smooth. There is a possibility that a flat metal ring seal of the type 10 may hang up on such a projection, interfering with the insertion of the tray 12 into the tower 18.
Another version of a known ring seal 20 is illustrated in FIG. 4. The resilient ring packing gland 20 is shown residing in a groove 22 of a tray 24 formed by a U-structure 26 about the periphery of the tray. The packing gland 20 is positioned within the groove 22 and the tray inserted within a tower wall 28. The packing gland 20 is a continuous gasket of fiberglass rope that is compressed between the groove 22 and the tower wall 28 to form a seal between the wall and the tray 24. As the tray 24 carrying the gasket 20 is lowered into the tower 28, the gasket is compressed locally by any projections encountered along the inner surface of the tower wall, allowing the gasket to slip be such projections. However, there still exists the possibility that the gasket 20, which has a generally rectangular cross section with a generally flat bottom, may hang up on such projections and even be pulled out of the groove 22 of the tray 24 by such projections.
It is advantageous and desirable to provide a packing tray ring seal that will seal completely around the periphery of the tray with no gaps, and that will pass along the interior surface of the tower wall without hanging up on projections or being dislodged by them. The present invention provides such a seal.